Hi J.,
I'm also a working mom, larger income in our family, only one kid and I like my job a lot sometimes, but there have been a few times that I felt that lack of passion and wondered if I could do something different.
It sounds like you aren't ready to give up the perks (and health benefits are a BIG perk) of your current job at this point, so I would spend time making very specific plans about the future.
First of all, are there any jobs with your current employer that you think you could feel more passionate about? If so, would your employer help you to gain the skills necessary to make a transfer into that position? If you've done good work for your manager, it can be worth expressing that you feel you need more challenge or more important projects.
Secondly, if that doesn't go anywhere, think about what kind of work would feel "worth it" to you, and how you can start to gain some exposure to that line of work now. If you are yearning to work for a more idealistic cause, can you find any time to volunteer for that cause now? Or find a few books on the subject, or a seminar? If you can start to make your future plans more concrete, that might help you keep sane until the kids are a bit older and larger changes are possible.
Good luck, and here's to finding passion in all aspects of our lives!